Nineteen occurrences of interspecific sexual behavior between male southern sea otters (Enhydra lutris nereis) and juvenile Pacific harbor seals (Phoca vitulina richardsi) were reported in Monterey Bay, California, between 2000 and 2002. At least three different male sea otters were observed harassing, dragging, guarding, and copulating with harbor seals for up to 7 d postmortem. Carcasses of 15 juvenile harbor seals were recovered, and seven were necropsied in detail by a veterinary pathologist. Necropsy findings from two female sea otters that were recovered dead from male sea otters exhibiting similar behavior are also presented to facilitate a comparison of lesions. The most frequent lesions included superficial skin lacerations; hemorrhage around the nose, eyes, flippers, and perineum; and traumatic corneal erosions or ulcers. The harbor seals sustained severe genital trauma, ranging from vaginal perforation to vagino-cervical transection, and colorectal perforations as a result of penile penetration. One harbor seal developed severe pneumoperitoneum subsequent to vaginal perforation, which was also observed in both female sea otters and has been reported as a postcoital lesion in humans. This study represents the first description of lesions resulting from forced copulation of harbor seals by sea otters and is also the first report of pneumoperitoneum secondary to forced copulation in a nonhuman animal. Possible explanations for this behavior are discussed in the context of sea otter biology and population demographics., Marine Mammals, Birds & Turtles, ,

Hair is used to determine trace elements exposure and status of pinnipeds because it is an excretory route for many elements and can be collected non-lethally. Despite increased use, there have been few studies on how sampling designs and procedures (e.g., hair type, collection site) affect results. The objective of this study was to determine whether concentrations of an essential (selenium; Se) and non-essential element (mercury; Hg) differed between hair samples collected from two body locations on harbor seals (Phoca vitulina). Concentrations of Se and total Hg (THg) differed between mid-dorsal midline and neck samples, and although the absolute differences were relatively small (Δabsolute Se=0.69μgg-1, Δabsolute THg=2.86μgg-1), the relative differences were large (Δrelative Se=49%, Δrelative THg=17%). These differences highlight the need to standardize the collection site for trace element determination in pinnipeds., Marine Mammals, Birds & Turtles
Harbor Seals

Abundance, seasonal distribution and population composition of balaenopterid whales in the Canal de Ballenas, Gulf of California, Mexico,

Description

Blue whales Balaenoptera musculus were most abundant in April and May while minke B. acutorostrata whales were equally abundant throughout the year. Fin B. physalus and Bryde's whales B. edeni were found but fin whales were more abundant in winter and spring; numbers were negatively correlated with water temperature. Bryde's whales were more abundant in summer and fall; numbers were positively correlated with water temperature. The percentage of identified individual adults that were females with calves was 10.6 for Bryde's and 2.7 for fin whales., Cited By (since 1996):13, , , Marine Mammals, Birds & Turtles

Most Eschrichtius robustus behavior involved apparent benthic feeding. There was little socializing by whales in July, but more in late September. Percent of time at the surface was about 21% in July and 23% in September. There were fewer blows per surfacing, shorter surface times, and shorter dive times when whales were not feeding than when they were feeding. Intervals between successive blows were longer in nonfeeding whales, but number of blows per minute did not differ between feeding and nonfeeding whales. Number of blows per surfacing and duration of surfacing increased with increasing water depth (from <20-80m). Dive duration did not change appreciably with depth in July, but did so in September. Blow rates by feeding whales increased in deeper water, indicating the need for whales to respire more as depth of dives increased. Time of day affected surfacing-dive respiration characteristics differently in different months. Whales fed more from 1800-2100 local Bering Sea time than at other times of day. During an average surfacing, feeding whales moved approx 50m; during a dive, net horizontal movements were 90-100m. Speed averaged 2km/h and was twice as fast at the surface (3.4km/h) compared with net underwater speed (1.7km/h)., Cited By (since 1996):12,
Marine Mammals, Birds & Turtles, ,

Identification photographs of humpback whales Megaptera novaeangliae, collected off Kauai during the years 1989 to 1993, were used to estimate population abundance off the Hawaiian Islands, USA. A total of 790 different individuals (988 different observations) were identified during the study. Several mark-recapture procedures were applied to the data using closed population models (Chapman's modified Petersen, weighted mean of the Petersen, Darroch's maximum likelihood estimator [MLE], and Chao's M(t), M(h), and M(th) estimators) and an open population model (Fisher-Ford estimator). The majority of population estimates were between 2000 and 5000 animals, with broad and overlapping 95% confidence intervals. Inconsistencies in pair-wise Petersen estimates and poor fit to the Fisher-Ford model indicated that the population of individuals was not identical for each sampling occasion. As a primary example of this, it is suggested that individuals captured in 1992 had a lower probability of capture in other years examined. Possibly the greatest problems in estimating abundance of this population dealt with temporary emigration and non-random mixing of the population between sampling occasions. After considering the range of estimates, and potential biases in the data set, I suggest that the abundance of humpback whales off the Hawaiian Islands is likely close to 4000 individuals, and most probably between 3000 and 5000. These estimates are considerably greater than those generated in the late 1970s and early 1980s and, if accurate, would indicate growth of the population over the past decade; however, it is strongly recommended that more representative and precise estimates be obtained for management purposes., Cited By (since 1996):21, Marine Mammals, Birds & Turtles, CODEN: MESED, ,

Maneuverability is critical to the performance of fast-swimming marine mammals that use rapid turns to catch prey. Overhead video recordings were analyzed for two sea lions (Zalophus californianus) turning in the horizontal plane. Unpowered turns were executed by body flexion in conjunction with use of the pectoral and pelvic flippers, which were used as control surfaces. A 90° bank angle was used in the turns to vertically orient the control surfaces. Turning radius was dependent on body mass and swimming velocity. Relative minimum radii were 9-17% of body length and were equivalent for pinnipeds and cetaceans. However, Zalophus had smaller turning radii at higher speeds than cetaceans. Rate of turn was inversely related to turn radius. The highest turn rate observed in Zalophus was 690 degrees s-1. Centripetal acceleration measured up to 5.1 g for Zalophus. Comparison with other marine mammals indicates that Zalophus has a morphology that enhances instability, thus providing enhanced turning performance. Enhanced turning performance is necessary for sea lions to forage after highly elusive prey in structurally complex environments., Cited By (since 1996):29, Marine Mammals, Birds & Turtles, CODEN: JEBIA, ,